1. Field
The presently disclosed subject matter relates to a method for position judgment, and an apparatus for judging distance. The device and method can be used whenever a position (i.e., a location which is determined based on whether an object is located at a far position and/or at a position at a relatively near position) of a moving object can be judged by emitting lights towards it. The disclosed subject matter is particularly suitable for use in a vehicle, a robot, security system and the like.
2. Description of the Related Art
A conventional method for a distance and/or position measurement that can be employed in a vehicle and the like is disclosed, for example, in patent document No. 1 (Japanese Patent Application Laid Open JP2005-182137), patent document No. 2 (Japanese Patent Application Laid Open JP2000-75030), etc. The disclosed conventional method is: emitting lights using EHF (extremely high frequency) radar, a laser radar, etc., towards an object; detecting the reflex light dashed against the object; and calculating the distance and/or position by measuring a time from emitting the light to detecting the reflex light. The above disclosed conventional method is well known as “Time of Flight” (TOF) method.
A distance measurement apparatus using the TOF method can exactly measure a distance from an object thereto. However the measurement accuracy depends on an operating speed of a photo-detector that detects a reflex light. Consequently, when a solid state camera is used as a photo-detector, the solid state camera is required to photograph an object with high speed. However, a solid state camera that allows measuring a distance as described above, such as a high-speed camera that can photograph an object with high speed, is expensive. Thus, a method for distance judgment using the TOF method along with the above described high-speed camera may result in some problems, such as high cost, inaccuracy if the camera is not quick enough, etc.
In addition, when a laser light source is used as a light source in a distance judgment apparatus, a driver is required to create an oscillation thereof. In addition, an output characteristic thereof should also be adjusted in order to prevent people that may be located in a direction of the distance judgment from being affected by the laser light source. Thus, the configuration including the driver and the adjustor may further result in complicating the apparatus.    1. Patent document No. 1: Japanese Patent Application Laid Open JP2005-182137    2. Patent document No. 2: Japanese Patent Application Laid Open JP2000-75030
The presently disclosed subject matter has been devised to consider the above and other problems, features and characteristics. Thus, according to an aspect of the disclosed subject matter, an embodiment of the disclosed subject matter can include a method for position judgment relating to whether an object is located at a location that is further or nearer based on previous object location determinations for the moving object. The method can have a simple configuration and be realized at low cost. Another embodiment of the disclosed subject matter can include a position judgment apparatus using or performing the immediately above described method. The position judgment apparatus can judge whether a moving object is getting nearer or moving further away with a simple configuration and a low cost, and can have practical uses related to a vehicle, a robot, security system, and the like.